Pick-proof locking system

Abstract

A pick-proof u-bolt type lock is disclosed with an untypical location for containing its cylinder lock. A tube, comprising a housing, has openings near its ends that accept the ends of a shackle which are secured within that housing. A cylinder lock is located between the shackle openings and an access port is provided to it for insertion and withdrawal of the key. A matching port on a collar that rotates around the housing is positioned to shut off that access, or to allow it selectively. Cooperating parts attached to, and effecting the operation of the lock, work to make the lock inoperable while access to the keyhole is available; and allow normal function of the lock when rotation of the collar prevents access. The key is not turned by finger grip, but instead, affecting the closure, turns the key and plug operating the cylinder lock and releasing the shackle at one end. The remaining end is freed as it swings clear of a securing pin in the other end of the housing. An enclosed operating key may continue to remain attached to an outside device, such as a key ring, a narrow slot through which the connection may pass is provided on the perimeter of the access port.

What is claimed is: 
     
       1. A pick-proof lock assembly comprising: a shackle having two legs;   a tubular collar having a central aperture;   a tubular housing having a central access aperture therein and further having lateral apertures for receiving the legs of said shackle;   said collar being rotatably mounted around said housing between a first position preventing access to said housing aperture and a second position wherein said collar aperture and said housing aperture are aligned;   a key;   a support means mounted in the housing;   a lock cylinder mounted on the support means, said lock cylinder having a first end including a key slot and a second end including an axial extension, said first end being accessible only through said housing access aperture;   a latch pin supported by said lock cylinder;   a shackle lock pin mechanically connected to said latch pin, said shackle lock pin being received in one leg of said shackle in a locked position and being retracted from said shackle in the unlocked position;   a spring biased retainer latch associated with the second end of said lock cylinder, pivoted in the housing and adapted to secure said shackle lock pin in locked position, while forcing said lock cylinder to rotate and be held in an extreme limit of rotation opposite the direction necessary to open the lock;   whereby upon insertion of said key into said key slot and upon rotational movement of said collar from said second position to said first position, said shackle lock pin moves from said locked position to said unlocked position, freeing said shackle for removal from said housing.   
     
     
       2. The lock assembly of claim 1 wherein said support means is adapted to slide in the axial direction within said housing between locked and unlocked positions, and a restoring spring is provided which returns said support means from the locked to unlocked position. 
     
     
       3. The lock assembly of claim 2 wherein said assembly is caused to be locked by pushing upon the first end of said lock cylinder, causing sliding movement of said support means with consequent engagement of one leg of said shackle by said shackle lock pin. 
     
     
       4. The lock assembly in claim 3 wherein a fixed pin within said housing engages one end of the said shackle not engaged by said shackle pin as said shackle is tilted in reference to its locked position in said housing, inserted into one of the two said lateral apertures and uprighted again. 
     
     
       5. The lock assembly in claim 4 wherein a minimally sized slot in the edge of either or both the overlapping portions of said access apertures in said collar and said housing in said first position that prevent access to said housings interior allow a link to exist between the key within a closed housing aperture and an object outside the entire lock assembly.